1. Field of the Invention
The present invention relates to a light emitting device, particularly to a light emitting device suitable for backlight of liquid crystal display or the like.
2. Description of the Related Art
Surface light emitting apparatus, constituted from side-view type light emitting device and a light guide plate that spreads light emitted by the light emitting device into a beam having planar intensity distribution, is used as the backlight of liquid crystal display or the like. As one type of side-view type light emitting device suitable for the surface light emitting apparatus, such a low-profile light emitting device is known that has light emitting diodes disposed in a recess of a resin package having flat configuration (for example, refer to Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2004-363537; and Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2007-27761).
A surface light emitting apparatus is constituted, in case the light emitting device of Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2004-363537; and Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2007-27761 is combined with the light guide plate, a plurality of light emitting devices are typically disposed along the longitudinal direction of light receiving surface of the light guide plate. However, in the case of the light emitting device of Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2004-363537; and Japanese Unexamined Patent Unexamined Publication (Kokai) No. 2007-27761, it is supposed that light emitted by the light emitting element disposed in the package does not spread sufficiently along the longitudinal direction of the light receiving surface of the light guide plate. As a result, portions between adjacent light emitting devices may remain dark, thus leading to unevenness in luminance called the firefly phenomenon, in which bright and dark portions are observed in the vicinity of the light receiving surface of the light guide plate.
While the unevenness in luminance may be eliminated by spreading the light emitted by the light emitting device uniformly over the entire light guide plate by using the light guide plate made in such a configuration that does not cause unevenness in luminance, such a light guide plate requires high manufacturing cost.
Another method of eliminating the unevenness in luminance is to dispose a large number of light emitting elements that are not packaged along the longitudinal direction of the light receiving surface of the light guide plate, although this method requires it to provide a larger number of light emitting elements for one light guide plate, thus resulting in higher cost.